These files are part of the dataset
"Historical built-up areas (BUA) - gridded surfaces for the U.S. from 1810 to 2015",
contained in the dataverse �HISDAC-US: Historical Settlement Data Compilation for the United States� 
(https://dataverse.harvard.edu/dataverse/hisdacus).

Reference:
Uhl, Johannes H.; Leyk, Stefan, 2020, "Historical built-up areas (BUA) - gridded surfaces for the U.S. from 1810 to 2015", 
https://doi.org/10.7910/DVN/J6CYUJ, Harvard Dataverse. 

The gridded surfaces (*.tif) contained in the BUA.tar.gz archive represent built-up areas (1) versus not built-up areas (0)
within grid cells of 250x250m, for each half-decade from 1810 to 2015. A grid cell is considered built-up if it contains at least one built-up property in a given year.
Moreover, there is a file called BUA_contemp.tif which contains all built-up grid cells,
regardless the value or availability of the built year attribute. Thus, BUA_contemp.tif represents the spatial distribution of built-up 
grid cells approximately in 2016, when the underlying ZTRAX data were compiled.

Abbreviations and explanations:
BUA:			Built-up areas. Grid cells containing at least one built-up property in a given year.

Data source: Zillow Transaction and Assessment Dataset (ZTRAX) (c) Zillow Inc.
Spatial resolution: 250m
Coordinate reference system:
USA Contiguous Albers Equal Area Conic USGS version (SR-ORG:7480)
https://spatialreference.org/ref/sr-org/usa_contiguous_albers_equal_area_conic_usgs_version-2/
Proj4: +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23.0 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs

Contact:
Stefan Leyk
Department of Geography
University of Colorado Boulder
GUGG 110, 260 UCB 
Boulder, CO 80309-0260, United States of America
stefan.leyk@colorado.edu